Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California

Abstract

As a result of extensive gold and silver mining in the Mojave Desert, southern California, mine wastes and tailings containing highly elevated arsenic (As) concentrations remain exposed at a number of former mining sites. Decades of weathering and erosion have contributed to the mobilization of As-enriched tailings, which now contaminate surrounding communities. Fluvial transport plays an intermittent yet important and relatively undocumented role in the migration and dispersal of As-contaminated mine wastes in semi-arid climates. Assessing the contribution of fluvial systems to tailings mobilization is critical in order to assess the distribution and long-term exposure potential of tailings in a mining-impacted environment. Extensive sampling, chemical analysis, and geospatial mapping of dry streambed (wash) sediments, tailings piles, alluvial fans, and rainwater runoff at multiple mine sites have aided the development of a conceptual model to explain the fluvial migration of mine wastes in semi-arid climates. Intense and episodic precipitation events mobilize mine wastes downstream and downslope as a series of discrete pulses, causing dispersion both down and lateral to washes with exponential decay behavior as distance from the source increases. Accordingly a quantitative model of arsenic concentrations in wash sediments, represented as a series of overlapping exponential power-law decay curves, results in the acceptable reproducibility of observed arsenic concentration patterns. Such a model can be transferable to other abandoned mine lands as a predictive tool for monitoring the fate and transport of arsenic and related contaminants in similar settings. Effective remediation of contaminated mine wastes in a semi-arid environment requires addressing concurrent changes in the amounts of potential tailings released through fluvial processes and the transport capacity of a wash.

Pollution Assessment of Heavy Metals in Soils and Plants around a Molybdenum Mine in Central China

“…Heavymetal pollution has become a serious environmental problem around mining areas [1][2][3]. Studies of heavymetal pollution in mining areas have mainly focused on the mined elements [4]; the associated heavy metals, which are important environmental pollutants that lower the mining grade, have mostly been ignored.…”

Distance to human populations influences epidemiology of respiratory disease in desert tortoises

“…In contrast to M. agassizii, for M. testudineum, the only other important predictor was distance to playas and agricultural fields, which, like distance to a human population centroid, was also negatively associated with prevalence. Playas are sinks and potential concentration areas for toxicants transported by wind and water from mines, roads, and other disturbed areas (Chaffee and Berry 2006;Kim et al 2012Kim et al , 2014. Agricultural fields are treated with fertilizers and chemicals.…”

Synthesis, characterization, and thermodynamics of arsenates forming in the Ca-Fe(III)-As(V)-NO3system: Implications for the stability of Ca-Fe arsenates

“…Arseniosiderite and yukonite were reported in gold ores and mine tailings occurring as secondary alteration products after arsenopyrite, arsenian pyrite, or arsenate minerals such as scorodite (Paktunc et al 2003(Paktunc et al , 2004. Ca-Fe arsenates were also reported in naturally contaminated soils at the Mokrsko-west gold deposit (Filippi et al 2007;Drahota et al 2009), impacted soil near an industrial site in France (Cancès et al 2008), mine tailings and contaminated soils at several abandoned gold mine sites in Nova Scotia (Walker et al 2009), mine wastes in the Mojave desert (Kim et al 2012), and historic gold mine wastes at Empire Mine State Historic Site, California (Burlak 2012). Arseniosiderite was also inferred to be present in mine tailings at the Lava Cap mine, Nevada (Foster et al 2011).…”